In an electrophotographic imaging process a dry toner (xe2x80x9ctonerxe2x80x9d) is fused to a sheet of imaging media (such as paper or a transparency, for example) to generate an image on the imaging media. This process is well understood in the art, and is accomplished using an electrophotographic imaging apparatus such as a printer, a photocopier, a facsimile machine, or a multi-function apparatus which performs one or more of the processes of printing, photocopying, or printing facsimiles. Toner is typically provided to an imaging producing section of the imaging apparatus from a toner reservoir, which can be a removable toner cartridge or a replenishable reservoir which is resident within the imaging apparatus.
Toner generally includes color particles (generally microscopic particles such as carbon or colored plastic). Toner can also include carrier particles. In certain instances, the color particles are capable of carrying an electrostatic charge, allowing them to be moved by an electrostatic process from the toner reservoir to an image producing section of the imaging apparatus. In other applications, the carrier particles carry an electrostatic charge to thereby facilitate movement of the color particles. (It should be noted that by xe2x80x9ccolorxe2x80x9d we mean to include black, as well as other colors.)
In the electrophotographic imaging process toner is moved from a toner reservoir to the image producing section of the imaging apparatus. The image producing section includes a photosensitive conductor, or photoconductor, which is typically a drum or a roller. The photoconductor can be selectively exposed by an energy source, such as a pulsed laser, to electrostatically produce a portion of an image on the photoconductor. Toner particles from the toner reservoir are then either repelled or attracted to the photoconductor, based on the relative electrostatic charge differential there between. For example, if a photoconductor is initially charged with a positive electrical charge and then portions thereof are exposed to produce a lesser positive charge (or a neutral or negative charge), then positively charged toner will be attracted to the exposed areas, and repelled from the non-exposed areas. The toner is then electrostatically transferred from the photoconductor to either a sheet of imaging media, or to an intermediate transfer carrier (such as a belt or a drum) which subsequently transfers the toner to imaging media. The toner is then fused to the sheet of imaging media in a fusing section of the imaging apparatus, and the media is then deposited in an output tray. The imaging apparatus thus further includes a media transfer section to facilitate movement of the imaging media from a media supply point to the toner transfer point, and thence to the fusing section and the output tray. Because toner generally is made from near-microscopic particles, it takes on the form of a powder. The toner resident within a toner reservoir will thus tend to settle and densify over time due to gravity. However, for the electrophotographic imaging process to be particularly effective, the toner needs to be available to the photoconductor in an essentially fluidic state during the imaging process. Fluidizing the toner allows better distribution of the toner over the photoconductor, and also helps to ensure that any carrier particles are well distributed among color particles. Accordingly, most toner reservoirs include an agitator which agitates or xe2x80x9cstirsxe2x80x9d the toner at least during the electrostatic imaging process.
To better understand the present invention, a brief reference will be made to a conventional prior art developing device using a toner cartridge, shown in FIG. 1. As depicted, a toner cartridge 1 stores a toner (not shown) therein. The cartridge 1 has a casing or housing 2 which defines a toner reservoir 19, and which accommodates an agitator 3 and a magnetic roller 4. The agitator 3 is rotated to agitate the toner existing in the housing 2. The housing 2 is formed with a plurality of toner outlets 5, only one of which can be seen in FIG. 1. A developing device 6 has a casing 7 which includes a toner storing section, or hopper as referred to hereinafter, 8. An agitator 9 is rotatable in the hopper 8 for agitating the toner existing in the hopper 8. A toner inlet 10 is formed in a portion of the casing 7 which faces the toner outlets 5 of the housing 2. A developing roller 11 causes the toner to deposit thereon. A doctor blade 12 causes the toner to form a thin layer on the surface of the developing roller 11. An intermediate roller 13 is held in contact with the developing roller 11, so that the toner is transferred from the developing roller 11 to the intermediate roller 13. A photoconductive element in the form of a drum 14 is held in contact with the intermediate roller 13. The toner is transferred from the intermediate roller 13 to the drum 14 in order to develop a latent image electrostatically formed on the drum 14. The resulting toner image is transferred from the drum 14 to a paper or similar recording medium xe2x80x9cMxe2x80x9d by an image transfer unit 15. A cleaning unit 16 cleans the surface of the drum 14 after the image transfer. A charger 17 uniformly charges the surface of the drum 14. An exposing device 18 exposes the charged surface of the drum 14 imagewise so as to form the latent image.
The agitator 3 of the toner cartridge 1 of FIG. 1 can be provided with a flexible blade 20 which can conform to the shape of the interior of the housing 2 as the agitator 3 rotates in the direction indicated by the arrows. While some toner cartridges have toner reservoirs with complex interior shapes, generally the cross sectional shape of the toner reservoir area can be described as non-square in cross section. This non-square geometry helps to maintain contact between the flexible blade 20 and the walls of the toner reservoir. Accordingly, toner storage volume in the toner reservoir is impacted by not being able to use a geometry that is more square or rectangular in cross section than prior art toner reservoirs. That is, it is not always possible to maximize the toner storage volume within the available space in a toner cartridge, since prior art toner reservoirs are generally configured to ensure that prior art agitators will be able to access the entire toner reservoir. Put another way, toner cartridges are typically configured to fit within an imaging apparatus based on the presence of ancillary components located within the imaging apparatus. The exterior dimensions imposed on a toner cartridge by these ancillary components thus define a maximum toner reservoir volume which can be achieved in a toner cartridge. Yet prior art toner agitators do not always allow the maximum available volume to be utilized due to the need to accommodate the limitations of prior art agitators.
In addition to toner cartridges which do not include the photoconductor (as depicted in FIG. 1), other prior art toner cartridges are known which incorporate the photoconductor. One such example is depicted in FIG. 2, which shows a toner cartridge 30 having a housing 31 which defines a toner reservoir 32 in which is located an agitator 34. Toner from within the toner reservoir 32 egresses through outlet opening 35 to a hopper area 36. An application roller 38 applies toner from the hopper area 36 to the optical photoconductor (xe2x80x9cOPCxe2x80x9d) 40, which has been charged by charge roller 42. A scraper blade 44 removes any residual toner from the OPC 40 after toner has been transferred from the OPC 40 to a sheet of imaging media (not shown), and the residual toner is stored in a waste storage area 46. Agitator 34 of toner cartridge 30 is depicted in a front view in FIG. 3. As can be seen, the agitator 34 includes two blade portions 50 which are supported by, but distal from, a central shaft 48, thus creating open areas 52. The open areas 52 allow the toner to xe2x80x9cfluffxe2x80x9d or volumize as it is agitated, rather than merely being pushed around inside the toner reservoir 32 (FIG. 2).
Other types of prior art toner agitators are known. For example, U.S. Pat. No. 5,307,129 shows a spiral toner agitator, and U.S. Pat. No. 5,305,064 shows a toner agitator which includes a rotating tube with holes disposed in the tube to allow toner to pass in and out of the holes as the toner is agitated.
In addition to generally limiting the geometry of the toner reservoir, prior art toner agitators do not always produce an even distribution of toner at the location where the toner is transferred out of the toner reservoir. This can result in uneven distribution of the toner on the OPC, and consequently a printed image of uneven color density.
What is needed then is a toner reservoir agitator which achieves the benefits to be derived from similar prior art devices, but which avoids the shortcomings and detriments individually associated therewith.
One embodiment of the present invention provides for a toner cartridge which includes a housing which defines a toner reservoir. A rotatable endless belt is located within the toner reservoir. The belt can be used to agitate or stir toner which can be placed in the toner reservoir. In one example the belt has periodic openings in the belt to allow toner to pass through the belt so that agitated toner can be provided to toner distribution components which can be present within, and/or outside of, the toner cartridge.
Another embodiment of the present invention provides for an imaging apparatus having a toner reservoir housing which defines a toner reservoir. A rotatable endless belt is disposed within the toner reservoir in the manner described in the paragraph immediately above. Yet another embodiment of the present invention also provides for a toner supply system which is resident within an imaging apparatus. In this latter embodiment, the toner supply system has a toner reservoir and a rotatable endless belt which is located within the toner reservoir. The belt can be used to agitate toner within the toner reservoir.
In one non-limiting example of the present invention the rotatable endless belt is supported by a drive roller which can be used to cause the belt to rotate within the toner reservoir. The belt can also be supported by additional rollers, which can be driven or idle. The belt can also be driven by, and supported by, other means.